Hand held computing devices, “palmtops”, or “palmhelds”, personal digital assistants (PDAs), or hand held computers typically weight less than a pound and fit in a pocket. These palmhelds generally provide some combination of personal information management, database functions, word processing, and spreadsheets. Because of the small size and portability of palmhelds, strict adherence to hardware constraints, such as sound generation hardware, must be maintained. It is conventional to use a sound generator in a palmheld device which is configured to operate ideally at a particular single frequency, rather than across a broad audio frequency range. When the sound generator is used across the audio frequency range, it provides “poor sound quality” with a widely varying sound pressure level over the audio frequency range for the same user setting.
Other conventional implementations of sound generation circuits include a dynamic speaker that is designed to operate across an audio frequency range having a substantially flat frequency response across the range. Such dynamic speakers are physically larger and cost many times more than sound generators. Further, the dynamic speaker drive circuit is also more complicated and expensive to implement than simple sound generators.
Accordingly, there is a need for a compact sound generator circuit that utilizes a software pre-filter to improve sound quality over an audible frequency range. Further, there is a need for a method of pre-filtering sound generator circuit signals in order to provide improved sound quality using a compact sound generator circuit.
The teachings herein below extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above mentioned needs.